1. Field
The present invention relates to an optical scanning device, and more particularly to an optical scanning device which scans a radiated optical flux by making use of predetermined oscillations of a resonance-type deflection element, an image display device provided with the optical scanning device and a retinal scanning display provided with the optical scanning device.
2. Description of the Related Art
With respect to an optical scanning device which constitutes a laser printer, an image display device or the like, in the related art, there has been known an optical scanning device which uses a resonance-type deflection element capable of scanning an optical flux by making use of oscillations.
For example, JP-A-2005-181477 (patent document 1) discloses an image display device capable of performing scanning on an optical flux radiated from a light source in a high-speed scanning direction (horizontal direction) using a resonance-type deflection element. The optical flux scanned by the resonance-type deflection element is scanned by a deflection element arranged in a succeeding stage in a low-speed scanning direction (vertical direction), and is projected on a retina of an eye thus forming an image on the retina.
Here, it is necessary for this type of optical scanning device to scan optical fluxes such that positions of the optical fluxes (scanning positions) corresponding to respective pixels (dots) in the scanning direction of the optical fluxes are arranged at equal intervals. However, when the resonance-type deflection element is used as a scanning element, in radiating the optical fluxes of the respective pixels at equal time intervals, the positions of the optical fluxes after scanning respective pixels are arranged at non-equal intervals in a sinusoidal shape.
In view of the above, in the related art, the optical fluxes of the respective pixels which are arranged at non-equal intervals by scanning using the resonance-type deflection element are optically corrected by an arcsin θ correction lens. Here, “pixel” in this specification indicates a minimum unit of an image signal and, more particularly, indicates a minimum unit of a digitalized image signal. That is, out of image signals, the image signal which is read corresponding to each dot is referred to as a pixel (a pixel signal).
However, the optical correction in the related art using the arcsin θ correction lens requires an expensive optical system thus pushing up a cost of an optical scanning device, and has a disadvantage that it is impossible to miniaturize the optical scanning device. To overcome such drawbacks, there has been known a method which constitutes an optical scanning device without using the arcsin θ correction lens. That is, this method uses clocks for pixel scanning (dot clocks) as cycles corresponding to the optical scanning directions.
JP-B-5-3947 (patent document 2) discloses an optical scanning device which includes an oscillator which generates master clocks, and a first frequency divider which generates position control clocks by dividing the master clocks, wherein dot clocks are generated based on the position control clocks, and the dot clocks are changed corresponding to scanning speeds of a resonance-type deflection element.
However, in the optical scanning device disclosed in patent document 2, since the dot clocks are changed corresponding to the scanning speeds of the resonance-type deflection element, the optical fluxes are scanned such that the scanning positions of the respective pixels are arranged at equal intervals. However, in the optical scanning device disclosed in patent document 2, the intensities of optical fluxes radiated for respective pixels in response to the dot clocks are not changed.
In view of the above, in Japanese Patent Application 2006-114713, the inventor of the present invention proposed a technique which allows an optical scanning device to maintain quality of an image without using an arcsin θ correction lens.